A-216 If it’s not broken, don’t fix it – determining best practices in POC INR testing

Abstract Background Our institution uses outpatient coumadin clinics to monitor patients’ INR values. A waived point of care (POC) device is used for patient testing. FDA guidance from 2018 recommends providers send blood samples for laboratory for PT/INR re-testing when POC INR results exceed 4.5 units, due to a positive bias in POC INR test results above that level. However, the IFU for our waived device has never reflected this FDA guidance, and our SOP remains unchanged regarding this recommendation. The lab director and POC team is considering limiting the reportable range to a maximum of 4.5 units versus adding a comment to every result above 4.5 that recommends the follow-up testing using a lab-based method. Before deciding on how to best proceed, it was important to understand our current practices and risks. Methods We gathered all INR results obtained in 2024 from our POC middleware system and matched INR results with results obtained from the coagulation laboratory to determine 1) the frequency of POC INR results above 4.5; and 2) whether lab-based testing was utilized as recommended follow-up. Results We had tested 84,569 patient samples for INR by waived POC testing in 2024. Of those results, 3126 results (3.7%) were above an INR of 4.5 units. We found that many patients with high POC INR results were re-tested by the same POC method on the same day. However, only 34 of these 3126 high INR values (1.1%) were followed up the same day with a lab-based PT/INR test. Review of these 34 paired results showed the positive bias of POC results, consistent with what has been demonstrated by other investigators. Conclusion It is clear that guidance regarding lab-based follow-up testing of high POC INR results has not been observed in our coumadin clinics. Despite this finding, we have not received clinical complaints of inaccurate test results or any indications of patient harm. We were limited as a quality project because we de-identified patient INR results early in this analysis; we were unable to look back in patient charts to understand the outcomes for patients with high POC INR results. However, by examining the sequence of follow-up testing after high POC INR results, our best guess is that patient management with or without follow-up lab testing is the same, i.e. hold/reduce coumadin doses and retest in two days instead of a week. The inconvenience of a lab draw and delay of getting a lab-based INR result may not be worth the added accuracy of the lab result. Further clinical input will be needed before altering our SOP in relation to this testing program.